This invention relates to a method and an apparatus for determining the position of a shift rail and more particularly, to a method and an apparatus for determining the linear and rotational position or orientation of a shift rail within a vehicle transmission system.
Shift rails are utilized within vehicle transmissions, such as automated manual transmissions, to selectively transfer or transmit movement from an actuator to one or more transmission shift members or forks in order to synchronize the engagement of the gears within the transmission. Automated manual transmissions typically include a transmission control system that selectively controls an actuator which selectively actuates the shift rail and which causes the shift rail to move in a linear direction and/or a rotational direction, thereby changing or altering the xe2x80x9cgear engagementxe2x80x9d of the transmission (e.g., the gear which is currently being used by the transmission).
In order to properly operate and control the transmission system, the current the gear engagement status or operating position of the transmission (e.g., whether the transmission is operating in xe2x80x9cfirstxe2x80x9d gear, xe2x80x9csecondxe2x80x9d gear, xe2x80x9cthirdxe2x80x9d gear, xe2x80x9cfourthxe2x80x9d gear, xe2x80x9cfifthxe2x80x9d gear, xe2x80x9csixthxe2x80x9d gear, xe2x80x9creversexe2x80x9d, or xe2x80x9cneutralxe2x80x9d) must be determined and communicated to the transmission control system. The current gear engagement status or position is typically determined by observing or measuring the linear and rotational position and/or orientation of the transmission shift rail. Particularly, the xe2x80x9crotationalxe2x80x9d position of the shift rail corresponds to and/or indicates the selection of a certain gear row or xe2x80x9cgatexe2x80x9d within the transmission gear box (e.g., the first/second gear gate, the third/fourth gear gate, or the fifth/sixth gear gate), while the xe2x80x9clinearxe2x80x9d position of the shift rail corresponds to and/or indicates the specific gear that is engaged within the selected row or gate.
Several methods, systems and apparatuses have been utilized to determine the position of the shift rail within these types of transmission systems. These prior shift rail position detecting methods, systems and apparatuses typically utilize an xe2x80x9coffset leverxe2x80x9d which is fixedly connected to a portion of the transmission shift rail, and which linearly and rotationally moves with the shift rail. These offset levers typically include a series of wires and/or angled portions that are physically and electrically coupled to one or more sensors which are disposed within the transmission housing. The sensors measure and/or detect the position and/or movement the offset lever the physical and electrical contact between the sensors and the offset lever. The sensors generate and communicate one or more electrical signals to the transmission control system or a portion of the transmission control system, which utilizes the received signals to determine the position of the shift rail and the present gear engagement of the transmission.
These prior methods, systems and apparatuses for determining the position of a shift rail suffer from several drawbacks. For example and without limitation, the sensors utilized by these prior systems must directly and physically contact the offset lever in order to determine the spatial orientation or position of the offset lever. To achieve this direct and physical contact between the sensors and the offset lever, additional and relatively complex moving connectors or connecting components must be produced and/or provided which undesirably increase the overall production cost of the transmission system. Furthermore, the contact between the offset lever, sensors, and the associated connecting components subjects these parts to potential wear, fatigue, and malfunction, which can lead to the overall xe2x80x9cbreakdownxe2x80x9d and/or failure of the shift rail position detection system or apparatus.
There is therefore a need for a new and improved method and apparatus for determining the position of a transmission shift rail which overcomes many, if not all, of the previously delineated drawbacks of prior shift rail position detection methods, systems and apparatuses.
It is a first object of the invention to provide a method and an apparatus for determining the position of a transmission shift rail which overcomes at least some of the previously delineated drawbacks of prior shift rail position detection methods, systems and apparatuses.
It is a second object of the invention to provide a method and an apparatus for determining the position of a transmission shift rail which minimizes the overall cost required to accurately determine the position of a transmission shift rail.
It is a third object of the invention to provide a method and an apparatus for determining the position of a transmission shift rail which eliminates and/or reduces the amount of moving and/or contacting parts which are required to determine the position of the shift rail.
According to a first aspect of the invention, an apparatus for measuring the position of a shift rail is provided. The shift rail is contained within a transmission assembly having a housing. The apparatus includes a member which is disposed around the shift rail and which has at least one surface; at least one sensor which is disposed within the housing, which remotely measures a distance between the at least one surface and the at least one sensor, and which selectively generates a signal having a value based upon the distance; and a controller which is communicatively coupled to the at least one sensor and which receives the signal. The controller is effective to determine the position of the shift rail based upon the value of the signal.
According to a second aspect of the invention, a method for determining the position of a shift rail is provided. The method includes the steps of: providing a member having at least one surface; providing at lease one proximity sensor; mounting the member to the shift rail; disposing the at least one proximity sensor remote from the at least one surface; remotely measuring the distance from the at least one sensor to the at least one surface; and determining the position of the shift rail based upon the measured distance.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.